On a mostly listless Tuesday at the Renee and Henry Segerstrom Concert Hall, Conrad Tao sat at his dressing room piano in casual street clothes and played a snippet of the world's most terrifying piece of music.

The 19-year-old closed his eyes and looked serene at first, swaying gently on the bench and letting his wrists rise and fall as if massaging the empty space above the keyboard. When the music turned hard and fast, his expression tightened and a tremor shot through his neck. Within a minute, his face twitched noticeably and neck jerked from side to side, his fingers pulsing downward as if stabbing the music.

The piece Tao was demonstrating didn't earn its formidable reputation because of unnerving chords or scandalous lyrics — it's instrumental, after all. Rather, Rachmaninoff's Piano Concerto No. 3, known colloquially as the Rach 3, has been renowned over the years for the difficulty it takes to perform.

The Pacific Symphony, which will host Tao in its first concert of the 2013-14 Classical Series this week, bills the Rach 3 as "one of the repertoire's most powerful, most demanding and most popular works."

And that's an understatement compared to some. The British newspaper the Guardian once dubbed it "the world's toughest piano piece." The Oscar-winning biopic "Shine" — whose accuracy has admittedly been questioned — implies that performing the work helped drive pianist David Helfgott to a mental breakdown.

So an interview with Tao inevitably leads to one question: Is the Rach 3 really as hard as people say?

Considering that Tao has been playing the piece for more than a quarter of his life, perhaps it's also inevitable that the answer isn't yes or no.

"You know, it has such a reputation for being so difficult, and very virtuosic, very soloistic, which it is," said the New York resident. "It is all those things, but one of the things I think is overlooked is how much of a dialogue the piece is between piano and orchestra, and how nuanced it is."

The first pianist to publicly play the Rach 3 was the composer himself, who finished it in 1909 and debuted it in New York. Josef Hofmann, the pianist to whom Rachmaninoff dedicated the work, is said to have died on playing it in concert. Others who tackled it in later years include Van Cliburn, Vladimir Horowitz, Martha Argerich and Olga Kern.

Nina Scolnik, a lecturer and associate chair for performance in UC Irvine's music department, said the piece is remarkable above all for its multiple threads, which a performer must work carefully to tie together. She added that the difficulty many pianists encounter with the Rach 3 may also come down to a simple factor: anatomy.

"Rachmaninoff had very large spaces between his fingers in addition to having very, very large hands," she said. "So the writing very much reflects his own body. In other words, the way he wrote his musical language is in some ways governed by how the instrument felt under his own hands and fingers."

When Tao began studying the concerto at age 14, he said, it took him a few months to learn the fast, dense notes. Once he had accomplished the technical side, he began the process of "digging" — finding emotional depth and resonance in the roughly 40-minute piece.

Still, the Columbia-Juilliard student doesn't dismiss the physical trial of playing the Rach 3. And though he hasn't seen "Shine," he understands its reputation among casual listeners.

"If you want to look at the last movement, as an example, I think you could make the argument that people are responding to the number of notes per minute," Tao said. "And in true Rachmaninoff fashion, there are passages where the writing is so thick. As the saying goes, if we were paid per note, we would all be playing Rachmaninoff."

Whatever the pay scale, Tao is excited to make his third appearance with the Pacific Symphony. The season's opening classical show, which runs Thursday through Saturday, features the Rach 3 along with Boyer's Festivities and Brahms' Symphony No. 4. (Tao will not play on the latter two.) Music director Carl St.Clair, who has conducted the Rach 3 several times, said he has looked forward to hearing Tao's interpretation of it.

"He always brings a very unique and a very fresh viewpoint and a very fresh look at these towering sort of masterwork concerti, and that's one of the reasons I enjoy performing with him," St.Clair said.

Tao, who first joined the Pacific Symphony as a replacement in 2011, has had ample time to develop that style. He recalls first playing the piano at the age of 18 months and learning to perform children's songs by ear. At 12, he signed with the management company IMG Artists, and Forbes ranked him two years ago on its "30 Under 30" list of young musicians shaping the industry.

By his count, Tao has now performed the Rach 3 in public up to half a dozen times. Still, he doesn't feel like he's mastered it yet.

"I don't expect this piece ever to become easy, and I don't want it to," he said. "Truth be told, it's become my instinct to be very suspicious when things get easy — because to me, that indicates self-satisfaction, which I think is extremely questionable and dangerous."